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Fatty acids (FAs) and other lipid molecules are important for many cellular functions, including vesicle exocytosis. For the pancreatic beta-cell, while the presence of some FAs is essential for glucose-stimulated insulin secretion, FAs have enormous capacity to amplify glucose-stimulated insulin secretion, which is particularly operative in situations of beta-cell compensation for insulin resistance. In this review, we propose that FAs do this via three interdependent processes, which we have assigned to a "trident model" of beta-cell lipid signaling. The first two arms of the model implicate intracellular metabolism of FAs, whereas the third is related to membrane free fatty acid receptor (FFAR) activation. The first arm involves the AMP-activated protein kinase/malonyl-CoA/long-chain acyl-CoA (LC-CoA) signaling network in which glucose, together with other anaplerotic fuels, increases cytosolic malonyl-CoA, which inhibits FA partitioning into oxidation, thus increasing the availability of LC-CoA for signaling purposes. The second involves glucose-responsive triglyceride (TG)/free fatty acid (FFA) cycling. In this pathway, glucose promotes LC-CoA esterification to complex lipids such as TG and diacylglycerol, concomitant with glucose stimulation of lipolysis of the esterification products, with renewal of the intracellular FFA pool for reactivation to LC-CoA. The third arm involves FFA stimulation of the G-protein-coupled receptor GPR40/FFAR1, which results in enhancement of glucose-stimulated accumulation of cytosolic Ca2+ and consequently insulin secretion. It is possible that FFA released by the lipolysis arm of TG/FFA cycling is partly "secreted" and, via an autocrine/paracrine mechanism, is additive to exogenous FFAs in activating the FFAR1 pathway. Glucose-stimulated release of arachidonic acid from phospholipids by calcium-independent phospholipase A2 and/or from TG/FFA cycling may also be involved. Improved knowledge of lipid signaling in the beta-cell will allow a better understanding of the mechanisms of beta-cell compensation and failure in diabetes. [ABSTRACT FROM AUTHOR]

Objective: To investigate the association of timing of commencing glucose management with glycemia, glycemic variability, and pregnancy outcomes among women with early gestational diabetes mellitus (GDM)., Research Design and Methods: In this substudy among participants of a trial of immediate vs. delayed treatment of early GDM diagnosed by 2013 World Health Organization criteria, all women treated immediately and those with delayed diagnosis at 24-28 weeks' gestation (treated as if late GDM) were instructed to monitor capillary blood glucose (BG) four times a day (fasting and 2-h postprandial) until delivery. Optimal glycemia was defined as ≥95% of BG measurements between 70 and 140 mg/dL (3.9-7.8 mmol/L)., Results: Overall, 107,716 BG values were obtained from 329 of 549 (59.9%) women (mean age 32.3 ± 4.9 years, BMI 32.0 ± 8.0 kg/m2, 35% European, gestation at GDM diagnosis 15.2 ± 2.4 weeks). Women treated early (n = 213) showed lower mean glucose (MG) and mean fasting glucose (MFG) compared with those treated late (n = 116) (MG: 5.7 ± 0.4 vs. 5.9 ± 0.5, P < 0.001; MFG: 5.2 ± 0.3 vs. 5.3 ± 0.4, P = 0.004), with greater optimal glycemia (74.6% vs. 59.5%, P = 0.006) and similar glycemic variability. MG was similar from 30 weeks' gestation. Overall, optimal glycemia was achieved in 69% of women and associated with lower birth weight, fewer large-for-gestational-age infants (14.4% vs. 26.7%, P = 0.01), more small-for-gestational-age infants (15.3% vs. 5.9%, P = 0.02), and lower gestational weight gain (4.9 ± 6.4 vs. 7.6 ± 6.2 kg, P = 0.001). Suboptimal glycemia was associated with non-European ethnicity, prior GDM, 1-h glucose at booking oral glucose tolerance test, and insulin use., Conclusions: Both early and delayed treatment of early GDM resulted in similar glycemia toward the end of pregnancy. Early treatment was associated with improved glycemia overall., (© 2024 by the American Diabetes Association.)

Objective: To compare pregnancy outcomes among women with a normal oral glucose tolerance test (OGTT) before 20 weeks' gestation (early) and at 24-28 weeks' gestation (late) (no gestational diabetes mellitus, or No-GDM), those with early GDM randomized to observation with a subsequent normal OGTT (GDM-Regression), and those with GDM on both occasions (GDM-Maintained)., Research Design and Methods: Women at <20 weeks' gestation with GDM risk factors who were recruited for a randomized controlled early GDM treatment trial were included. Women with treated early GDM and late GDM (according to the World Health Organization's 2013 criteria) were excluded from this analysis. Logistic regression compared pregnancy outcomes., Results: GDM-Regression (n = 121) group risk factor profiles and OGTT results generally fell between the No-GDM (n = 2,218) and GDM-Maintained (n = 254) groups, with adjusted incidences of pregnancy complications similar between the GDM-Regression and No-GDM groups., Conclusions: Women with early GDM but normal OGTT at 24-28 weeks' gestation had pregnancy outcomes that were similar to those of individuals without GDM. Identifying early GDM likely to regress would allow treatment to be avoided., (© 2024 by the American Diabetes Association.)

Objective: We evaluated associations between early-pregnancy oral glucose tolerance test (OGTT) glucose and complications in the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) cohort to inform prognostic OGTT thresholds., Research Design and Methods: Individuals with risk factors for hyperglycemia were recruited for an international, multicenter, randomized controlled gestational diabetes mellitus (GDM) (World Health Organization 2013 criteria) treatment trial. A 2-h 75-g OGTT was performed at <20 weeks' gestation. Individuals with early treated hyperglycemia in pregnancy were excluded from the primary analysis. Early OGTT glucose concentrations were analyzed continuously and in glycemic categories (normal, low band, and high band)., Results: Overall, 3,645 individuals had an OGTT at (mean ± SD) 15.6 ± 2.5 weeks. For each 1-SD increase in fasting, 1-h, and 2-h glucose values, there were continuous positive associations with late GDM: adjusted odds ratio (aOR) 2.04 (95% CI 1.82-2.27), 3.05 (2.72-3.43), and 2.21 (1.99-2.45), respectively. There were continuous positive associations between 1-h and 2-h glucose and the perinatal composite (birth <37 + 0 weeks, birth trauma, birth weight ≥4,500 g, respiratory distress, phototherapy requirement, stillbirth/neonatal death, and shoulder dystocia), with aOR 1.15 (95% CI 1.04-1.26) and 1.14 (1.04-1.25), respectively, and with large-for-gestational-age offspring, with aOR 1.18 (1.06-1.31) and 1.26 (1.01-1.25), respectively. Significant associations were also observed between 1-h glucose and cesarean section and between fasting and 2-h glucose and neonatal hypoglycemia. In categorical analysis, only the high-band 1-h glucose (≥10.6 mmol/L [191 mg/dL]) predicted the perinatal composite., Conclusions: There is a continuous positive association between early-pregnancy OGTT glucose and complications. In individuals with hyperglycemia risk factors, only the high-glycemic-band 1-h glucose corresponded to increased risk of major perinatal complications., (© 2024 by the American Diabetes Association.)

Objective: In most gestational diabetes mellitus (GDM) studies, cohorts have included women combined into study populations without regard to whether hyperglycemia was present earlier in pregnancy. In this study we sought to compare perinatal outcomes between groups: women with early GDM (EGDM group: diagnosis before 20 weeks' gestation but no treatment until 24-28 weeks' gestation if GDM still present), with late GDM (LGDM group: present only at 24-28 weeks' gestation), and with normoglycemia at 24-28 weeks' gestation (control participants)., Research Design and Methods: This is a secondary analysis of a randomized controlled treatment trial where we studied, among women with risk factors, early (<20 weeks' gestation) GDM defined according to World Health Organization 2013 criteria. Those receiving early treatment for GDM treatment were excluded. GDM was treated if present at 24-28 weeks' gestation. The primary outcome was a composite of birth before 37 weeks' gestation, birth weight ≥4,500 g, birth trauma, neonatal respiratory distress, phototherapy, stillbirth/neonatal death, and shoulder dystocia. Comparisons included adjustment for age, ethnicity, BMI, site, smoking, primigravity, and education., Results: Women with EGDM (n = 254) and LGDM (n = 467) had shorter pregnancy duration than control participants (n = 2,339). BMI was lowest with LGDM. The composite was increased with EGDM (odds ratio [OR] 1.59, 95% CI 1.18-2.12) but not LGDM (OR 1.19, 95% CI 0.94-1.50). Induction of labor was higher in both GDM groups. In comparisons with control participants there were higher birth centile, higher preterm birth rate, and higher rate of neonatal jaundice for the EGDM group (but not the LGDM group). The greatest need for insulin and/or metformin was with EGDM., Conclusions: Adverse perinatal outcomes were increased with EGDM despite treatment from 24-28 weeks' gestation, suggesting the need to initiate treatment early, and more aggressively, to reduce the effects of exposure to the more severe maternal hyperglycemia from early pregnancy., (© 2024 by the American Diabetes Association.)

Objective: Preanalytical processing of blood samples can affect plasma glucose measurement because ongoing glycolysis by cells prior to centrifugation can lower its concentration. In June 2017, ACT Pathology changed the processing of oral glucose tolerance test (OGTT) blood samples for pregnant women from a delayed to an early centrifugation protocol. The effect of this change on the rate of gestational diabetes mellitus (GDM) diagnosis was determined., Research Design and Methods: All pregnant women in the Australian Capital Territory (ACT) are recommended for GDM testing with a 75-g OGTT using the World Health Organization diagnostic criteria. From January 2015 to May 2017, OGTT samples were collected into sodium fluoride (NaF) tubes and kept at room temperature until completion of the test (delayed centrifugation). From June 2017 to October 2018, OGTT samples in NaF tubes were centrifuged within 10 min (early centrifugation)., Results: A total of 7,509 women were tested with the delayed centrifugation protocol and 4,808 with the early centrifugation protocol. The mean glucose concentrations for the fasting, 1-h, and 2-h OGTT samples were, respectively, 0.24 mmol/L (5.4%), 0.34 mmol/L (4.9%), and 0.16 mmol/L (2.3%) higher using the early centrifugation protocol ( P < 0.0001 for all), increasing the GDM diagnosis rate from 11.6% ( n = 869/7,509) to 20.6% ( n = 1,007/4,887)., Conclusions: The findings of this study highlight the critical importance of the preanalytical processing protocol of OGTT blood samples used for diagnosing GDM. Delay in centrifuging of blood collected into NaF tubes will result in substantially lower rates of diagnosis than if blood is centrifuged early., (© 2020 by the American Diabetes Association.)

Stratifying the management of type 2 diabetes (T2D) has to take into account marked variability in patient phenotype due to heterogeneity in its pathophysiology, different stages of the disease process, and multiple other patient factors including comorbidities. The focus here is on the very challenging subgroup of patients with T2D who are overweight or obese with insulin resistance (IR) and the most refractory hyperglycemia due to an inability to change lifestyle to reverse positive energy balance. For this subgroup of patients with T2D, we question the dogma that IR is primarily harmful to the body and should be counteracted at any cost. Instead we propose that IR, particularly in this high-risk subgroup, is a defense mechanism that protects critical tissues of the cardiovascular system from nutrient-induced injury. Overriding IR in an effort to lower plasma glucose levels, particularly with intensive insulin therapy, could therefore be harmful. Treatments that nutrient off-load to lower glucose are more likely to be beneficial. The concepts of "IR as an adaptive defense mechanism" and "insulin-induced metabolic stress" may provide explanation for some of the unexpected outcomes of recent major clinical trials in T2D. Potential molecular mechanisms underlying these concepts; their clinical implications for stratification of T2D management, particularly in overweight and obese patients with difficult glycemic control; and future research requirements are discussed., (© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

Our objective was to determine if the insulin-sensitizing drug pioglitazone acutely reduces insulin secretion and causes metabolic deceleration in vivo independently of change in insulin sensitivity. We assessed glucose homeostasis by hyperinsulinemic-euglycemic and hyperglycemic clamp studies and energy expenditure by indirect calorimetry and biotelemetry in male Wistar and obese hyperinsulinemic Zucker diabetic fatty (ZDF) rats 45 min after a single oral dose of pioglitazone (30 mg/kg). In vivo insulin secretion during clamped hyperglycemia was reduced in both Wistar and ZDF rats after pioglitazone administration. Insulin clearance was slightly increased in Wistar but not in ZDF rats. Insulin sensitivity in Wistar rats assessed by the hyperinsulinemic-euglycemic clamp was minimally affected by pioglitazone at this early time point. Pioglitazone also reduced energy expenditure in Wistar rats without altering respiratory exchange ratio or core body temperature. Glucose-induced insulin secretion (GIIS) and oxygen consumption were reduced by pioglitazone in isolated islets and INS832/13 cells. In conclusion, pioglitazone acutely induces whole-body metabolic slowing down and reduces GIIS, the latter being largely independent of the insulin-sensitizing action of the drug. The results suggest that pioglitazone has direct metabolic deceleration effects on the β-cell that may contribute to its capacity to lower insulinemia and antidiabetic action.

Munc13-1 is a diacylglycerol (DAG) receptor that is essential for synaptic vesicle priming. We recently showed that Munc13-1 is expressed in rodent and human islet beta-cells and that its levels are reduced in islets of type 2 diabetic humans and rat models, suggesting that Munc13-1 deficiency contributes to the abnormal insulin secretion in diabetes. To unequivocally demonstrate the role of Munc13-1 in insulin secretion, we studied heterozygous Munc13-1 knockout mice (+/-), which exhibited elevated glucose levels during intraperitoneal glucose tolerance tests with corresponding lower serum insulin levels. Munc13-1(+/-) mice exhibited normal insulin tolerance, indicating that a primary islet beta-cell secretory defect is the major cause of their hyperglycemia. Consistently, glucose-stimulated insulin secretion was reduced 50% in isolated Munc13-1(+/-) islets and was only partially rescued by phorbol ester potentiation. The corresponding alterations were minor in mice expressing one allele of a Munc13-1 mutant variant, which does not bind DAG (H567K/+). Capacitance measurements of Munc13-1(+/-) and Munc13-1(H567k/+) islet beta-cells revealed defects in granule priming, including the initial size and refilling of the releasable pools, which become accentuated by phorbol ester potentiation. We conclude that Munc13-1 plays an important role in glucose-stimulated insulin secretion and that Munc13-1 deficiency in the pancreatic islets as occurs in diabetes can reduce insulin secretion sufficient to cause abnormal glucose homeostasis.

We previously reported decreased glucose-stimulated insulin secretion (GSIS) in hormone-sensitive lipase-null mice (HSL(-/-)), both in vivo and in vitro. The focus of the current study was to gain further insight into the signaling role and regulation of lipolysis in islet tissue. The effect of glucagon-like peptide 1 (GLP-1) on GSIS was also studied, as GLP-1 could augment GSIS via protein kinase A activation of HSL and lipolysis. Freshly isolated islets from fasted and fed male HSL(-/-) and wild-type (HSL(+/+)) mice were studied at ages 4 and 7 months. Neutral cholesteryl ester hydrolase activity was markedly reduced in islets from both 4- and 7-month-old male HSL(-/-) mice, whereas a marked deficiency in triglyceride lipase activity became evident only in the older mice. The deficiencies in lipase activities were associated with higher islet triglyceride content and reduced lipolysis at basal glucose levels. Lipolysis was stimulated by high glucose in islets of both wild-type and HSL-null mice. Severe deficiencies in GSIS were found, but only in islets from 7-month-old, fasted, male HSL(-/-) mice. GSIS was less affected in 4-month-old fasted male HSL(-/-) mice and not reduced in female mice. Exogenous delivery of free fatty acids (FFAs) rescued GSIS, supporting the view that the lack of endogenous FFA supply for lipid-signaling processes in HSL(-/-) mice was responsible for the loss of GSIS. GLP-1 also rescued GSIS in HSL(-/-) mice, indicating that signaling via HSL is not a major pathway for its incretin effect. Thus, the secretory phenotype of HSL-null mice is gender dependent, increases with age, and is influenced by the nutritional state. Under most circumstances, the major determinant of lipolytic flux in the beta-cell involves an enzyme(s) other than HSL that is acutely activated by glucose. Our results support the view that the availability of endogenous FFA through HSL and an additional enzyme(s) is involved in providing lipid moieties for beta-cell signaling for secretion in response to glucose.

Objective: To determine the value of measuring serum triglyceride (TG) levels early in pregnancy for predicting late-gestation glucose tolerance and neonatal birth weight ratio (BWR) (birth weight corrected for gestational age)., Research Design and Methods: The relationships between morning nonfasting TG measured early in pregnancy (gestational age 12 +/- 6 weeks [mean +/- SD]) and glucose tolerance measured by a 3-h 50-g oral glucose tolerance test (OGTT) late in pregnancy (gestational age 30 +/- 3 weeks) and BWR were investigated in 388 women attending routine antenatal care. The data were analyzed for all women in addition to subgroups of Australian/Western European-born (n = 246) and Asian-born (n = 97) women., Results: Morning nonfasting TG positively correlated with the OGTT glucose area under the curve (OGTT-GAUC) (r = 0.23, P < 0.0001) in all subjects. This correlation was stronger in the subset of subjects who had TG measured between 9 and 12 weeks of gestation (r = 0.35, P = 0.0001) and was particularly strong in Asian-born women who had TG measured within this period (r = 0.71, P < 0.0001). Mean TG and the 2- and 3-h OGTT values were higher in Asian-born subjects compared with Australian/Western European-born subjects (P = 0.004, P < 0.0001, and P = 0.02, respectively). TG correlated positively with BWR in all subjects (r = 0.12, P = 0.02), in Asian-born subjects (r = 0.23, P = 0.02), and in subjects with gestational diabetes mellitus (GDM) (r = 0.60, P = < 0.001)., Conclusions: TG, if measured between 9 and 12 weeks of gestation, has moderate predictive value for subsequent glucose tolerance in pregnancy. TG is also predictive of BWR in GDM subjects. Further studies are warranted to investigate the role of early TG measurement in the screening and management of GDM. Metabolic heterogeneity exists between Asian-born and Australian/Western European-born women, the significance of which is still unclear and warrants further study.

In 47 patients with diabetic nephropathy (29 type I, 18 type II) renal function and blood pressure (BP) (treated with or without an angiotensin-converting enzyme [ACE] inhibitor, enalapril [10 mg], in 38 hypertensive patients) were followed over 4 years. A percutaneous renal biopsy was performed in all patients initially and repeated in a representative 19 patients with treated hypertension after 4 years. Mean glomerular volume (MGV), interstitial fibrosis (IF), capillary volume, and sclerosed glomeruli (GS) were measured histomorphometrically. Mean fall in creatinine clearance (CCr) was 11.8% after 4 years with no difference between treatment groups or type of diabetes. BP both initially and during treatment correlated with initial and final serum creatinine and CCr (P < 0.01). There were no histomorphometric differences between type I and type II patients or hypertension treatment groups. Initial IF correlated with initial and final serum creatinine and CCr (P < 0.05) in all patients and type I patients alone, MGV correlated inversely with CCr in type I patients (P < 0.05). After 4 years, IF (24.8 vs. 30.0%, P < 0.01) and GS (26 vs. 37%, P < 0.05) increased significantly, and increase in IF correlated with fall in CCr (P < 0.01). Proteinuria and HbA1 did not correlate with indexes of function or structure. In this longitudinal study of patients with diabetic nephropathy, there was a close relation between BP and renal function but no difference between treatment with enalapril and other hypertensive agents. The correlations between renal function and histology at entry and after 4 years suggest that IF is a co-determinant of renal function in diabetic nephropathy.